Automatic schema upgrade in a big data pipeline

ABSTRACT

Disclosed are embodiments for providing batch performance using a stream processor. In one embodiment, a method is disclosed comprising receiving an event that includes a plurality of fields and extracting needed fields from the plurality of fields. The method then serializes the plurality of fields and generates a new event that includes the set of needed fields and a hidden field, the value of the hidden field comprising the serialized fields. The method then transmits the new event for processing using at least one processing stage of a stream processor. In response, the method reserializes a processed event generated by the stream processor and outputs the reserialized event to a downstream consumer.

COPYRIGHT NOTICE

This application includes material that may be subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent disclosure, as it appears in the Patent and Trademark Office files or records, but otherwise reserves all copyright rights whatsoever.

BACKGROUND

In the era of big data processing, data pipelines have become vital to ingesting, processing, and outputting large quantities of data at high velocity and having high variability. In general, a data pipeline comprises a series of automated processing stages that take raw input data and convert the raw input data into a more suitable format for consumption by downstream computer processing systems.

Various architectures of data pipelines exist, including batch, Lambda, and Kappa architectures. Batch data pipelines process data in “batches” at regular intervals and are suitable for non-critical functionality while providing high reliability of data processing. Batch data pipelines, however, suffer from not being able to process data in real-time. Thus, a lag behind the ingestion of data and output of useful information or knowledge always exists in a batch data pipeline.

Lambda pipelines utilize a batch processor concurrently with a stream processor. In these pipelines, the batch processor processes all data within a historical batch while the stream processor “augments” the processed batch data with the results of stream processing. Eventually, the batch processor will “re-process” the data processed by the stream processor and overwrite the information generated by the stream processor. Lambda pipelines are fast, due to the use of stream processors; however, they require duplication of processing logic in both the stream processors and the batch processors. Further, Lambda pipelines use twice the processing hardware due to the use of two separate processing paradigms (i.e., stream and batch, which process the data in the same manner).

Like Lambda pipelines, Kappa pipelines utilize a stream processor. However, Kappa pipelines eschew a batch processor. Kappa pipelines require frequent “re-running” of event streams through the stream processor to provide simulated batch performance. Kappa pipelines ensure that streaming data is processed correctly (e.g., the pipeline does not drop or duplicate data); however, these pipelines ensure this by re-executing processing and are thus slower than pure streaming pipelines. Further, since Kappa pipelines use stream processing techniques, there is no method for performing more complex operations such as joins or aggregations, since these operations inherently require access to a full (e.g., batch) dataset. That is, stream processors inherently cannot perform these operations, thus replaying streams does not remedy this problem.

BRIEF SUMMARY

This disclosure recognizes a need in the art for a new pipeline architecture that provides the advantages of stream processors (e.g., speed) with the advantages of batch processors (e.g., integrity and complex operations). The disclosed embodiments provide these advantages and solve other problems in existing pipelines.

The disclosed embodiments describe an improved big data processing system that uses a stream processing engine with additional hardware and software to harden inaccuracies detected during stream processing.

In one embodiment, a method is disclosed comprising: receiving an event, the event including a plurality of fields; extracting a set of needed fields from the plurality of fields; generating a plurality of serialized fields by serializing the plurality of fields; generating a new event, the new event including the set of needed fields and a hidden field, the value of the hidden field comprising the serialized fields; transmitting the new event to at least one processing stage of a stream processor; generating a reserialized event by reserializing a processed event generated by the stream processor, the processed event generated by the stream processor based on the new event; and outputting the reserialized event to a downstream consumer.

In another embodiment, a non-transitory computer-readable storage medium for tangibly storing computer program instructions capable of being executed by a computer processor, the computer program instructions defining the steps of: receiving an event, the event including a plurality of fields; extracting a set of needed fields from the plurality of fields; generating a plurality of serialized fields by serializing the plurality of fields; generating a new event, the new event including the set of needed fields and a hidden field, the value of the hidden field comprising the serialized fields; transmitting the new event to at least one processing stage of a stream processor; generating a reserialized event by reserializing a processed event generated by the stream processor, the processed event generated by the stream processor based on the new event; and outputting the reserialized event to a downstream consumer.

In another embodiment, an apparatus is disclosed comprising: a processor; and a storage medium for tangibly storing thereon program logic for execution by the processor, the stored program logic causing the processor to perform the operations of: receiving an event, the event including a plurality of fields; extracting a set of needed fields from the plurality of fields; generating a plurality of serialized fields by serializing the plurality of fields; generating a new event, the new event including the set of needed fields and a hidden field, the value of the hidden field comprising the serialized fields; transmitting the new event to at least one processing stage of a stream processor; generating a reserialized event by reserializing a processed event generated by the stream processor, the processed event generated by the stream processor based on the new event; and outputting the reserialized event to a downstream consumer.

The illustrated embodiments provide numerous benefits over existing pipelines. The disclosed embodiments reduce data processing and certification times by certifying events using a stream processor versus a batch processor. Thus, the illustrated embodiments, do not require a “waiting” period prior to certifying results and can certify results in real-time or near real-time. The disclosed embodiments additionally utilize a single pipeline and thus do not require the hardware duplication, software complexity, and human resources required by Lambda pipelines. Relatedly, since application-level code must only be deployed once, rapid changes in data processing can be implemented without requiring separate development workflows. Additionally, since only one codebase is used, there is no risk of variations in processing between pipelines. Finally, in existing pipelines, sacrifices for speed can lead to a more significant variation between the initially posted results from the streaming pipeline and the final results from batch processing. As the latency of batch increases relative to streaming, this can lead to a lack of confidence in reporting as the variation becomes more pronounced. The disclosed embodiments alleviate this deficiency.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1A is a block diagram illustrating a processing system employing a Lambda architecture.

FIG. 1B is a block diagram illustrating a processing system employing a Kappa architecture.

FIG. 2 is a block diagram illustrating a data processing system according to some embodiments of the disclosure.

FIG. 3 is a block diagram illustrating a pipeline factory according to some embodiments of the disclosure.

FIG. 4 is a block diagram illustrating a core pipeline according to some embodiments of the disclosure.

FIG. 5 is a flow diagram illustrating a method for processing events in a streaming pipeline to support automatic schema upgrades according to some embodiments of the disclosure.

FIG. 6A is a flow diagram illustrating a method for reserializing events in a streaming pipeline to support automatic schema upgrades according to some embodiments of the disclosure.

FIG. 6B is a flow diagram illustrating a method for processing explosion operations in a streaming pipeline to support automatic schema upgrades according to some embodiments of the disclosure.

FIG. 6C is a flow diagram illustrating an alternative method for processing explosion operations in a streaming pipeline to support automatic schema upgrades according to some embodiments of the disclosure.

FIG. 7 is a schematic diagram illustrating a computing device showing an example embodiment of a client or server device used in the various embodiments of the disclosure.

DETAILED DESCRIPTION

FIG. 1A is a block diagram illustrating a processing system employing a Lambda architecture.

In the illustrated embodiment, events in the system (100 a) originate from one or more event emitters (102). As used herein, an event refers to any type of data generated by a computing system. Generally, most events include arbitrary data as well as a timestamp indicating when the event emitter (102) generated the data. Alternatively, or in conjunction with the preceding, the system (100 a) adds a timestamp representing the time the pipelines (106, 108) receive the event. In some embodiments, the timestamp comprises a standard time (e.g., based on a 24-hour clock). In some embodiments, the timestamp comprises a numerical value (e.g., time since UNIX epoch). In other embodiments, the timestamp may comprise a sequence number or other incrementing (or otherwise changing) value. In some embodiments, events further include nonce values to ensure uniqueness.

The event emitters (102) can comprise any computing system capable of generating data. The disclosure places no limitations on the type of data or type of systems capable of generating such data. As one example, an event emitter may include a digital analytics system configured to track and monitor user events on webpages or in mobile apps. A digital analytics platform generates many events as users access products. One example is the delivery of advertising creatives. In these scenarios, the analytics platform generates an event indicating that a server transmitted the creative to the end-user. The analytics platform also generates an event indicating that the end-user device displayed the creative (i.e., an impression). If the end-user interacts with the creative, the analytics platform generates a “click” event (which may be any type of interaction including touch events and thus is not limited to physical mouse clicks). In certain embodiments, the analytics platform also generates conversion events that indicate that after an impression, and after a click, the end-user has completed another action (e.g., completes a digital purchase) that is related to the previous events. In some embodiments, the analytics platform tracks all of these events via a client-side identifier stored in, for example, a cookie or other end-user storage mechanism.

In some embodiments, event emitters (102) are part of the system (100 a). That is, in some embodiments, the system (100 a) includes and has some level of control over the event emitters (102). Examples of this type of arrangement include internal data sources for an organization (e.g., internal analytics tracking). In other embodiments, the event emitters (102) comprise third-party systems. In some embodiments, the system (100 a) receives events from both internal and external event emitters (102).

In either scenario, event emitters (102) transmit events over a transport layer (104). The transport layer (104) comprises one or more network protocols and one or more physical media used for transporting data. The disclosure does not unduly limit the structure of the transport layer. In some embodiments, the system (100 a) uses an Internet protocol suite (e.g., transmission control protocol (TCP) and Internet protocol (IP)) as the transport layer (104). The system (100 a) may use other models such as those adhering to the Open Systems Interconnection (OSI) model or other types of protocol models. In some embodiments, the transport layer (104) performs other operations on the events beyond network routing (e.g., TCP/IP). For example, the transport layer (104) may compress events using, as an example, gzip or other compression algorithms.

The specific internal workings of the transport layer (104) are not limiting, and the system (100 a) may ignore various features of the transport layer (104) that are handled entirely in the transport layer (e.g., congestion control in a TCP layer). However, as discussed in more detail herein, the transport layer (104) may include inherent data transfer characteristics that impact the processing of the data by systems. One example, discussed in more detail in FIG. 2 et seq, is that some transport layer (104) designs may unintentionally (or, in some cases, intentionally) duplicate events transmitted over a network. In such networks, the event emitters (102) transmit one event, but the pipelines (106, 108) receive two or more events. A more concrete example of such a transport layer is a publish-subscribe system such as Apache® Kafka, which can provide “at least once” delivery of events.

As illustrated, the system (100 a) routes events from the transport layer (104) to both a streaming pipeline (106) and a batch pipeline (108). In the illustrated embodiment, the batch pipeline (108) processes data in batches. As used herein, a batch refers to a period in which the batch pipeline (108) analyzes data (e.g., every hour). The disclosure does not describe the specific inner workings of the batch pipeline (108) in detail; however, the batch pipeline (108) comprises any processing system that provides accurate processing of data. Examples of batch pipelines include Hadoop clusters. The batch pipeline (108) ensures this accuracy by running slowly and at fixed intervals upon receiving all needed data. Since the batch pipeline (108) requires a fixed period of data (e.g., one hour) and a second fixed period to process the data (e.g., three hours), the batch pipelines (108) are consistently “behind” the current time. That is, when the batch pipeline (108) writes data to the data warehouse (110), the data written is “stale” by a fixed amount of time (e.g., four hours in the previous examples). However, as stated above, consumers of the batch-processed data can be confident that the data is accurate.

As a brief aside, before Lambda systems, big data systems often only included a batch pipeline (108) and did not include a streaming pipeline (106). As a result, such systems produced consistently delayed results. To remedy this delay, the system (100 a) includes a streaming pipeline (106). Such a pipeline may comprise one or more stream processors such as Apache® Storm processors or similar stream processors. In contrast to the batch pipeline, the streaming pipeline (106) processes data in real-time or near real-time. Thus, when the streaming pipeline (106) receives an event over the transport layer (104), it immediately processes or transforms the event and writes the processed event to the data warehouse (110).

Since the streaming pipeline (106) processes events quickly and in isolation, the streaming pipeline (106) may introduce errors in the processed data. For example, the streaming pipeline (106) generally does not guard against writing duplicate data if the pipeline (106) receives duplicate events. Similarly, the streaming pipeline (106) may inadvertently drop some events. Thus, the streaming pipeline (106) is fast but inaccurate.

In the illustrated embodiment, the data warehouse (110) segments data received from the streaming pipeline (106) and the batch pipeline (108) into two separate storage areas. Additionally, as the batch pipeline (108) “catches up” to the data processed by the streaming pipeline (106), the data warehouse (110) overwrites the results of the streaming pipeline (108). Thus, at any given moment, the data warehouse (110) stores accurate, batch-processed data and a smaller, more recent subset of inaccurate stream-processed data. Absent system failures, the size subset of the inaccurate data remains constant while the size of the accurate data increases over time.

To support the above format of the data warehouse, the system (100 a) must duplicate logic between the streaming pipeline (106) and the batch pipeline (108). Since the streaming results must be “reconciled” with the results of the batch processing, the streaming pipeline (106) and batch pipeline (108) must process the events in the same manner. This requirement doubles both the development time and the computing resources needed to support both pipelines (106, 108). Additionally, the system (100 a) requires additional software and hardware to enable the data warehouse (110) to perform the reconciliation process after the completion of each batch processing job.

FIG. 1B is a block diagram illustrating a processing system employing a Kappa architecture. The illustrated system (100 b) solves some of the problems of Lambda architectures, as discussed in the preceding figure. However, the system (100 b introduces additional problems and fails to provide full batch support.

Various elements of the system (100 b) are identical, or nearly identical, to those similarly numbered elements of FIG. 1A. The event emitters (102) and the data transport layer (104) perform the same functions as previously described. Also, the streaming pipeline (106) may perform many, if not all, of the same operations of the streaming pipeline (106) discussed in FIG. 1A.

As illustrated, the streaming pipeline (106) receives events generated by the event emitters (102) over the data transport layer (104). The streaming pipeline (106) processes this data and writes the processed data to the data warehouse (116). In contrast to the data warehouse (110) in FIG. 1A, the data warehouse (116) may only include a single storage area for data given the absence of a batch processing layer.

As described in the description of the previous system (100 a), streaming pipelines (106) generally cannot guarantee the accuracy of data processing. Some systems (e.g., 100 b) remedy this problem by employing “micro batching” whereby small batches of stream events are processed simultaneously. In general, these batches represent milliseconds of events, thus providing reasonable speed while simulating small batches. Micro-batching, however, fails to provide the level of accuracy provided by larger (e.g., one hour) batches. Another technique uses recompute logic (114) to re-process streaming events when the logic of the streaming pipeline (106) changes or based on other requirements. In this scenario, the system (100 b) can store raw events in the raw events storage module (112), the recompute logic (114) retrieves these events. The recompute logic (114) then streams the events into the stream pipeline (106) for re-processing. In one scenario, the recompute logic (114) executes when the system (100 b) changes the processing logic of the streaming pipeline. Thus, if the system (100 b) modifies how the streaming pipeline (106) processes events, the recompute logic (114) simulates a historical event stream. In another embodiment, the recompute logic (114) can stream data from the raw events storage module (112) to the streaming pipeline (106) at fixed intervals, thus simulating a batch processing mode. However, there are numerous challenges to this approach that limit its effectiveness. First, data from the raw events storage module (112) must be re-streamed in the same order as streamed initially, to ensure the integrity of the re-processing. Thus, the recompute logic (114) reproduces inaccuracies relating to out-of-order events during the re-streaming. Second, the infrastructure that supports the streaming pipeline (106) generally cannot handle significant increases in streaming data, thus limiting the total amount of re-streamed data the streaming pipeline (106) can handle at any given time. Third, and most importantly, the streaming pipeline (106) cannot inherently perform various operations that a batch pipeline (108) can perform, such as joins or aggregations. Thus, even if re-streamed, the output of the streaming pipeline (106) always lacks these advanced operations.

FIG. 2 is a block diagram illustrating a data processing system according to some embodiments of the disclosure.

The illustrated system (200) segments the data processing into multiple logical layers. In some embodiments, these layers may also comprise physical layers, with each layer physically connected via a network interconnect. The illustrated layers comprise serving (220 a), data transport (220 b), pipeline factory (220 c), packaging (220 d), and warehousing (220 e) layers.

The serving layer (220 a) includes one or more event emitters (202). In the illustrated embodiment, these event emitters (202) can be similar or identical to the event emitters (102) discussed previously. As a few examples, the event emitters (202) can comprise systems including, but not limited to, ad servers, web servers, and beacon servers, that produce raw traffic events and send the events factory layer (220 c) via the data transport layer (220 b). In the illustrated embodiment, the data transport layer (220 b) represents the previously described data transport (204). In the illustrated embodiment, the data transport layer (220 b) comprises multiple network topologies and protocols that, when combined, deliver events to the factory layer (220 c).

In the illustrated embodiment, the factory layer (220 c) receives raw events from the data transport layer (220 b) and processes the events via a core pipeline (210). The description of FIG. 3 provides further detail regarding the factory layer (220 c), and the description of FIG. 4 provides further detail regarding the core pipeline (210). Thus, the following description of the factory layer (220 c) only briefly describes the layer (220 c) and the core pipeline (210), and FIGS. 3 and 4 present further detail.

The factory layer (220 c) is responsible for doing the bulk of the processing of event traffic via the core pipeline (210). The following description describes exemplary processing operations performed by the core pipeline (210). The core pipeline (210) may perform some or all of the following operations as well as additional operations.

In one embodiment, in the serving (220 a) and data transport (220 b) layers, devices often compress and bundle data to conserve bandwidth. As a result, the core pipeline (210) may perform a parsing operation that unpacks or processes complex data structures (e.g., blobs) so that downstream consumer systems can access the data. Thus, as one example, the core pipeline (210) can detect that an incoming event was compressed using a gzip algorithm and may first unzip the event.

In another embodiment, the core pipeline (210) performs explosion operations. An explosion operation comprises unpacking composite events. For example, a multi-serve event comprises an event indicating that an end-user device received a set of content to be displayed. Thus, the multi-serve event comprises a data structure describing multiple items of content (e.g., advertisements). The core pipeline (210) may transform a single multi-serve event into multiple single-serve events such that each item of content in the event is associated with an independent event for later processing.

In another embodiment, the core pipeline (210) performs metadata annotation operations. As illustrated, the core pipeline (210) communicates with a metadata store (208). In one embodiment, the metadata store (208) comprises a data storage device such as a MySQL database or other type of relational database. In other embodiments, the metadata store (208) may comprise other types of data storage devices (e.g., a key-value data store). The core pipeline (210) accesses the metadata store (208) to perform dimensional annotation on incoming event data. As used herein, dimensional annotation refers to the augmenting of data with additional other data. For example, a content serving event may only a line item identifier identifying the served content. The core pipeline (210) may access the metadata store (208) and look up a parent insertion order, an advertiser identifier, and an organization for that line item identifier. The core pipeline (210) may then augment the line item identifier with this metadata to generate an annotated event. In this way, downstream consumer systems can group and aggregate based on the line item identifier.

In another embodiment, the core pipeline (210) performs traffic annotations. A traffic annotation comprises a complex join of an event with a prior event. For example, a click event may need to be joined with a first impression event to annotate the click with auction information or targeting information that is only available in the first impression.

In another embodiment, the core pipeline (210) performs arbitrary computations dictated by business logic. An example of this type of computation is a currency conversion. By doing the operation only once in the core pipeline (210), the system (200) can ensure consistency across all subsequent consumer systems, rather than requiring downstream consumer systems to implement the same rules and possibly arrive at different results.

In another embodiment, the core pipeline (210) validates incoming events. In this embodiment, the core pipeline (210) can filter events based on traffic conditions.

In another embodiment, the core pipeline (210) performs deduplication on incoming events. As discussed previously, the data transport layer (220 b) may support “at least once” semantics. Alternatively, or in conjunction with the preceding, event emitters may allow duplicate events. Regardless of the source of duplication, the core pipeline (210) ensures that all events are processed and stored once and not duplicated. For example, the core pipeline (210) may allow more than one click event per impression event during a given period.

In another embodiment, the core pipeline (210) performs normalization on the received events. During a normalization operation, the core pipeline (210) “fits” an event to a particular schema or layout to facilitate reporting. This schema or layout is typically a standard field alignment and transformation.

Finally, in some embodiments, the core pipeline (210) performs a fast feedback operation. In this operation, the core pipeline (210) provides feeds or streams of data at very low latency to low-latency consumers (206) such as an ad serving budget control system. Typically, most consumer systems wait until the core pipeline (210) has completed all processing steps; however, some consumer systems are willing to sacrifice quality for timing. These specialty stages can be critical to some consumer systems.

In general, the core pipeline (210) processes events linearly: the quality of the event data increases as data passes from one processing operation to the next. Ultimately, after the core pipeline (210) applies all operations to the event data, the core pipeline (210) writes the processed event to one or more fact feeds (212). In the illustrated embodiment, a fact feed (212) comprises a log of every event that was received by the core pipeline (210) and any additional information that the core pipeline (210) annotates or computes. The fact feeds (210) become the source of truth for the entire system (200). By having the core pipeline (210) compute the fact feed (212) used by subsequent consumers pipelines (214 a, 214 b, 214 n), the overall quality of the system (200) is improved.

Since the system uses a centralized fact feed (212), the core pipeline (210) never removes any field from an event. Additionally, the core pipeline (210) does not modify any raw field that it receives from the core pipeline (210) from the data highway (204). However, as one exception, the core pipeline (210) may replace null or empty fields with a static or default value, as this may assist downstream consumer systems (214 a, 214 b, 214 n). In most embodiments, the core pipeline (210) does not attempt to “correct” or “fix” invalid values in an event. However, the core pipeline (210) may deviate from this requirement to recover from failed launches or bugs. In some embodiments, if the core pipeline (210) violates this requirement and fixes an invalid value in an event, the core pipeline (210) annotates the record with a flag so that a downstream consumer system can monitor the rule.

Importantly, the core pipeline (210) also ensures that no event is duplicated in the final fact feed (212). Thus, the core pipeline (210) never intentionally duplicates or allows duplicate events to result from the operations.

In the illustrated embodiment, the packaging layer (220 d) comprises various consumer pipelines (214 a, 214 b, . . . 214 n) retrieve or receive data from the fact feed (212). The packaging layer (220 d) accesses the fact feed (212) and provides the processed events therein to downstream consumer pipelines (214 a, 214 b, . . . 214 n). Whereas the factory layer (220 c) is typically a complex, but linear processing stage, the packaging layer (220 d) is typically composed of multiple parallel consumer pipelines (214 a, 214 b, . . . 214 n). Consumer pipelines (214 a, 214 b, . . . 214 n) are typically minimal, possibly single-stage pipelines that project and aggregate the events in the fact feed (212) for loading into a warehouse (e.g., 218 a, 218 b, . . . 218 n) or similar system. The availability of the fact feed (212) triggers consumer pipelines (214 a, 214 b, . . . 214 n), and thus the consumer pipelines (214 a, 214 b, . . . 214 n) may run in parallel with one another.

In some instances, the consumer pipelines (214 a, 214 b, . . . 214 n) are external to the factory layer (220 c) and warehouse layer (220 e). In other instances, the system (200) includes and controls the consumer pipelines (214 a, 214 b, . . . 214 n). Alternatively, or in conjunction with the preceding, the warehousing layer (220 e) may be external to the system (200). In various embodiments, the consumer pipelines (214 a, 214 b, . . . 214 n) generally perform some or all of the following operations (or combinations thereof).

In one embodiment, the consumer pipelines (214 a, 214 b, . . . 214 n) perform mapping and transformation operations. In these operations, the consumer pipelines (214 a, 214 b, . . . 214 n) may require the data in a format different than the format of the fact feed (212). For example, the consumer pipelines (214 a, 214 b, . . . 214 n) may map enumerated values (possibly in a lossy fashion) to fit a further downstream consumer data model.

In another embodiment, the consumer pipelines (214 a, 214 b, . . . 214 n) perform projection operations. In some embodiments, consumer pipelines (214 a, 214 b, . . . 214 n) will typically not require every field of the fact feed (212). Thus, the consumer pipelines (214 a, 214 b, . . . 214 n) only ingest a small fraction of the available columns.

In another embodiment, the consumer pipelines (214 a, 214 b, . . . 214 n) perform aggregation operations. In some embodiments, the consumer pipelines (214 a, 214 b, . . . 214 n) aggregate facts and produce metric fields for efficient loading into a database or similar data store.

In another embodiment, the consumer pipelines (214 a, 214 b, . . . 214 n) perform reverse annotation joins (e.g., right outer joins). In some embodiments, the consumer pipelines (214 a, 214 b, . . . 214 n) perform join operations that cannot be implemented efficiently within the core pipeline (210). For example, a data science consumer pipeline may require a feed containing every impression event joined to any future click events recorded in the fact feed (212). Because this type of pipeline requires data collected over a long period before processing can begin, it would negatively impact all consumer pipelines (214 a, 214 b, . . . 214 n) to wait. Therefore, the pipeline performs these joins in batch outside of the core pipeline (210).

In another embodiment, the consumer pipelines (214 a, 214 b, . . . 214 n) perform rollup operations. In some embodiments, the consumer pipelines (214 a, 214 b, . . . 214 n) may choose to create rollup feeds of the raw facts stored in fact feed (212). For example, the consumer pipelines (214 a, 214 b, . . . 214 n) may create an hourly feed from a five-minute fact feed. The consumer pipelines (214 a, 214 b, . . . 214 n) may perform this operation to use fewer filenames in a distribute filed system (e.g., the Hadoop Filesystem, HDFS) since such a file system collapses multiple files into larger single files. Further, the rollup may typically transform the data into a columnar format like Optimized Row Columnar (ORC) to promote faster ad hoc projection.

In another embodiment, the consumer pipelines (214 a, 214 b, . . . 214 n) perform sketch operations. In some embodiments, as the consumer pipelines (214 a, 214 b, . . . 214 n) generate aggregates, the consumer pipelines (214 a, 214 b, . . . 214 n) may produce aggregate sketch columns to capture unique users or similar complex computations. The consumer pipelines (214 a, 214 b, 214 n) can perform this expensive operation once on behalf of multiple end-users or downstream systems.

In another embodiment, the consumer pipelines (214 a, 214 b, . . . 214 n) perform cleansing operations. In some embodiments, the consumer pipelines (214 a, 214 b, . . . 214 n) may cleanse data in the fact feed (212) for a specific purpose. For example, cookies or personally identifiable information (PII) might need to be anonymized, or the consumer pipelines (214 a, 214 b, . . . 214 n) may need to obscure data to enforce data visibility controls.

In some embodiments, the consumer pipelines (214 a, 214 b, . . . 214 n) can be hierarchal. That is, a first consumer pipeline may perform one or more shared steps, and downstream consumer pipelines use the output of the first consumer pipeline as input.

After processing by consumer pipelines (214 a, 214 b, . . . 214 n), each of the consumer pipelines (214 a, 214 b, . . . 214 n) output further processed event data to respective data warehouses (218 a, 218 b, . . . 218 n) in the warehousing layer (220 e). The warehousing layer (220 e) is generally the final stage of the system (200), where data is loaded into various systems to facilitate reporting, billing, or analysis. A data team may be responsible for various aspects of the warehousing, or it may be delegated to a data customer instead. Operations for a data team include loading, replication, and verification. In loading operations, the system (200) may need to load the data into a data warehouse (e.g., an Oracle or Druid data warehouse) or place the data onto a shared drop box or similar system. In replication operations, the system (200) may need to replicate a data feed to another data processing (e.g., Hadoop) cluster in a different co-location. In a verification operation, the system (200) may need to verify that the data loaded into a warehouse (218 a, 218 b, . . . 218 n) accurately matches the original fact feed (210) (i.e. certify there was no data loss).

As illustrated, in some embodiments, data bypasses the packaging layer (220 d). In these embodiments, the core pipeline (210) streams output directly to a real-time data warehouse (216). In the illustrated embodiment, the real-time data warehouse (216). In the illustrated embodiment, the system (200) may use a real-time data warehouse (216) for reporting or similar functions that do not require high data accuracy.

FIG. 3 is a block diagram illustrating a pipeline factory according to some embodiments of the disclosure.

In the illustrated embodiment, a data highway (204) delivers events from one or more event emitters (not illustrated) to a factory layer (220 c) and raw event storage (302). The description of FIG. 2 provides further detail regarding the data highway (204) which is not repeated herein.

In the illustrated embodiment, the raw event storage (302) may comprise a distributed file system (e.g., HDFS). In one embodiment, the system (300) writes raw events to the raw event storage (302) as they are received. In some embodiments, the system (300) writes the raw events to raw event storage (302) in a batch mode. That is, the system (300) writes a separate file for each batch period (e.g., one hour), the file including all events received during that period. In some embodiments, not illustrated, external consumer systems can access the raw event storage (302) to perform batch processing. Thus, in some embodiments, the raw event storage (302) can be used to provide backwards compatibility with existing batch pipelines.

As illustrated, a stream processor (304) receives events from the data highway (204). In one embodiment, the stream processor (304) comprises a distributed stream processor. In one embodiment, the stream processor (304) comprises a streaming topology that defines data processing stages to perform on events.

One example of a stream processor (304) is an Apache® Storm topology. Briefly, a Storm topology is a graph of inputs and processing nodes. The topology receives events as input streams. Each event in the input stream comprises a tuple and the input stream itself is an unbounded series of such tuples. The topology receives streams from input sources, referred to as “spouts.” The topology performs all processing in individual processing nodes, referred to as “bolts.” The topology defines the input to a bolt as either a spout or another bolt. Thus, the topology defines connects between spouts and bolts. The output of one or more bolts forms the output of the topology.

In the illustrated embodiment, the stream processor (304) performs any or all of the processing operations described in the description of core pipeline (210) in FIG. 2 . Details of these operations are not repeated herein. Importantly, the stream processor (304) ensures that a given event received over the data highway (204) is output at most once to the streaming queue(s) (306). Thus, during processing, the stream processor (304) detects and drops any duplicated events. FIG. 4 provides further detail regarding specific techniques for performing this detection and dropping.

As illustrated, the stream processor (304) outputs the processed and de-duplicated event stream to one or more streaming queues (306). In one embodiment, the streaming queues (306) comprise one or more Apache® Kafka queues. Since the event stream is processed by the stream processor (304), the data stored in the streaming queues (306) can be considered as source of truth for downstream consumers. Thus, a low-latency consumer system (206) can directly access the streaming queues (306). In this manner, the system (300) can simulate a fully streaming pipeline. As will be discussed, since the stream processor (304) processes the event stream and ensures that no records are dropped or duplicated, the simulated stream in the streaming queues (306) is more accurate than a raw event stream. Furthermore, as will be discussed, the output of the stream processor (304) includes the results of more complicated or advance operations (e.g., joins or dimensional annotation) which are not possible using traditional stream processing techniques.

A spooler (308) and auditor (310) use the output of the stream processor (304) to support advanced operations by the stream processor (304). FIG. 4 provides more detail regarding the spooler (308) and reference is made to that description.

In one embodiment, the spooler (308) comprises a second stream processor. The spooler (308) ensures that a one-to-one mapping between streamed data and data written to the fact feed (210) exists. The spooler (308) also ensures that streaming events retrieved from the queues (306) appears exactly once in the fact feed (210) (i.e., no events in the queues, 306, are duplicated). As such, the spooler (308) may comprise a separate stream topology similar to the stream processor (304). In contrast to the stream processor (304), the spooler (308) reads events from the streaming queues (306). Thus, the event stream to the spooler (308) comprises the processed events. As illustrated, prior to writing to the fact feed (210), the spooler (308) outputs to the auditor (310) via a buffer (312). In one embodiment, the output of the spooler (308) comprises a flat file (e.g., an HDFS file) and the buffer (312) comprises a distributed file system such as RDFS. In one embodiment, this flat file comprises a set of events occurring in a given batch period. Thus, the flat file simulates batch processing, but using the streaming events.

In the illustrated embodiment, an auditor (310) receives the output of the spooler (308). As described above, in some embodiments, the output of the spooler (308) comprises a batch file of events. In the illustrated embodiment, the auditor (310) also accesses raw event storage (302). In one embodiment, the format of the raw event storage (302) and the output of the spooler (308) are the same. For example, spooler (308) may write flat files to HDFS buffer (312) and raw event storage (302) may comprise raw events stored in the same type of file (e.g., HDFS). In the illustrated embodiment, the auditor (310) retrieves a batch file from buffer (312). In one embodiment, this batch file is associated with a fixed period. In some embodiments, this fixed period is represented in the filename or in metadata. Using this fixed period, the auditor (310) then retrieves a set of events from the raw event storage (302) matching the fixed period. In one embodiment, the periods of the buffer (312) and the raw event storage (302) are synchronized. In this embodiment, the auditor (310) then retrieves a single file from the raw event storage (302) that matches the period pulled from the buffer (312). In other embodiments, the auditor (310) may execute a MapReduce job to identify events split across multiple files. In this embodiment, the periods represented by files in the raw event storage are not synchronized with the buffer (312). Thus, the auditor (310) must patch together portions of multiple files stored in raw events storage (302) to rebuild a period of raw events matching the period stored in the buffer (312). In either event, the auditor (310) receives two files containing raw events from raw event storage (302) and a set of processed events for the same period stored in buffer (312).

In general, the auditor (310) ensures that each processed event in the buffer (312) matches a raw event stored in raw event storage (302). Thus, the auditor (310) ensures that no events were dropped during processing by the stream processor (304) and that no events were duplicated. If the auditor (310) detects that an event exists in the raw event storage (302) and does not exist in the corresponding buffer (312) output, the auditor (310) sends the missing event back to the stream processor (304) for re-processing.

The stream processor (304) reprocesses the events using the same processing logic used to process the event originally. In some embodiments, the stream processor (304) may add a field to the reprocessed event to indicate it was (or will be) reprocessed. In most embodiments, the stream processor (304) will properly process the event during re-processing. However, if the stream processor (304) cannot reprocess the event (as detected by the auditor, 310), the system (300) may gracefully handle the error. In one embodiment, the auditor (310) can itself add a field to the raw event indicating that the raw event was not processed and write the event along with the processed events.

After any missing events are re-processed, the auditor (310) writes the final output to the fact feed (210). Since spooler (308), buffer (312) and auditor (310) operate on batches of events, the fact feed (210) comprises a simulated batch data store. In some embodiments, the auditor (310) will delay writing to the fact feed (210) until any events are re-processed. In other embodiments, the auditor (310) writes the partially final output file to the fact feed (210) and updates the file upon completing the re-processing.

FIG. 4 is a block diagram illustrating a core pipeline according to some embodiments of the disclosure. Various elements of FIG. 4 are described in the previous figures and those elements are not described again herein.

In the illustrated embodiment, a stream processor (304) receives events from a data highway (204). In the illustrated embodiment, the stream processor (304) receives events from the data highway (204) via an initial spout (404). The stream processor (304) as illustrated includes two separate spouts (404, 422). In the illustrated embodiment, the stream processor (304) utilizes two spouts (404, 422) to distinguish between event streams (e.g., original versus re-processing). In the illustrated embodiment, the stream processor (304) topology can be configured to add additional extract-transform-load (ETL) steps (e.g., bolts) for the reprocessing spout (422) versus events received via the initial spout (404).

In the illustrated embodiment, the stream processor (304) processes events received via spouts (404, 422) via ETL logic (406). As described previously, ETL logic (406) may comprise a series of linear processing stages (e.g., bolts) for each operation performed on events.

In the illustrated embodiment, the ETL logic (406) outputs processed events to two streaming queues (408 a, 408 b). In one embodiment, the two queues (408 a, 408 b) store varying types of event data. As illustrated, a first queue (408 a) is accessed by a partial stream consumer system (424). In the illustrated embodiment, the first queue (408 a) may be filled by the ETL logic (406) prior to the execution of all processing steps. In the illustrated embodiment, the ETL logic (406) may eschew more complicated and time-consuming operations and interrupt the full processing steps to provide low latency operations. In some embodiments, this bypassing includes foregoing joins, traffic protection, annotation, etc. In the illustrated embodiment, the partial stream consumer system (424) may comprise a fast feedback system such as budget or pacing systems that are willing to accept a certain level of error. Thus, the first queue (408 a) provides “best effort” data wherein the system (400) does not guarantee the accuracy of the data. In practice, however, the system (400) will generally process a large amount of data correctly enough that the best effort data in the first queue (408 a) is of value to the partial stream consumer system (424).

In contrast to the first queue (408 a), the stream processor (302) fills the second queue (408 b) with the results of the full ETL processing. Thus, the ETL logic (406) fully processes the data in the second queue (408 b), including performing joins, deduplication, annotations, fraud detection, traffic protection, etc. In one embodiment, the complete streaming consumer system (426) access second queue (408 b) can retrieve data that achieves close to exactly once performance (that is, no events are dropped or duplicated) since the data was fully processed in the ETL logic (406). In some embodiments, this performance will meet “exactly once” performance. However, in other embodiments, the output of the second queue (408 b) is still subject to inaccuracies caused by the underlying messaging queue. In some embodiments, a near exactly one completeness from second queue (408 b) comprises a 99.9% guarantee of completeness. Such a confidence level is often suitable for applications such as real-time reporting.

Finally, as illustrated and discussed above, a final fact feed (210) meets exactly once requirements of all systems and provide batch-like performance. That is, data in the fact feed (210) will be fully de-duplicated and ensure that no events were dropped. As discussed in FIG. 3 , this guarantee is implemented via spooler (308) and auditor (310). Auditor (310) is described more fully in FIG. 3 and those details are incorporated herein by reference.

In the illustrated embodiment, the spooler (308) is illustrated as including deduplication writer (412), deduplication store (414), and a fact feed writer (416).

In the illustrated embodiment, the deduplication writer (412) receives events from the second queue (408 b). An event is uniquely identified by an event identifier (event id). The spooler (308) considers two events as duplicates if they have the same event identifier. Events may include additional, but standardized, fields such as a type, timestamp, join status, and secondary event identifiers.

The deduplication writer (412) writes each of the events to deduplication store (414). In one embodiment, the store (414) comprises a database such as HBase or a similar storage device. Upon receiving an event, the writer (412) analyzes the fields associated with the event. If the event includes one or more secondary event identifiers, the writer (412) will retrieve all events stored in store (414) matching these secondary event identifiers and update the entries to indicate that a primary event is available (i.e., will be written to the store, 414). The writer (412) will then write the received event to the store (414) using the event identifier as a key. In some embodiments, a salt will be added to the event identifier before using the event identifier as a key. In the illustrated embodiment, the writer (412) will not write the event if the event has secondary event identifiers and the initial step of updating the secondary events is not successful. In some embodiments, the writer (412) will serialize the event prior to writing the event as a value for the event identifier key.

In the illustrated embodiment, the deduplication store (414) stores events per batch period and per type of event. In some embodiments, the store (414) creates a new table for each event type and batch period pair for a fixed period of time (e.g., one week) since the current time. The store (414) additionally includes a pruning process that periodically inspects the created tables and removes older tables not occurring within the current period (e.g., older than one week). In some embodiments, the auditor (310) initiates this pruning process upon confirming that all data for a given period is certified.

The spooler (308) additionally includes a fact feed writer (416). In the illustrated embodiment, the fact feed writer (416) waits for a signal from auditor (310) to trigger a spooling process to write the events in the store (414) to the fact feed (210) for a particular batch period and event type. In one embodiment, the fact feed writer (416) includes an internal web server that comprises a Hypertext Transfer Protocol (HTTP) endpoint that is called by the auditor (310) to initiate the spooling. As described above, once the auditor (310) confirms that the data in the store (414) is fully processed and certified, the auditor (310) issues a call to the endpoint which causes the writer (416) to start writing to the fact feed (210). In one embodiment, the writer (416) executes a distributed process routine to per from a full table scan of the store (414) and write the events to the fact feed (210).

For each event in the store (414), the writer (416) will deduplicate the events prior to writing. In one embodiment, the writer (416) will first determine if an event has one or more secondary identifiers and whether that secondary event was successfully joined to the event under inspection. If so, the writer (416) will select the most recent secondary event and write that joined event to the fact feed (210). Alternatively, if the event under inspection indicates that a primary event is available, the writer (416) will skip the event (since a root event exists). Finally, if the event does not have secondary identifiers and the primary event flag is not raised, the writer (416) will write out the event as failed since the secondary event was not properly joined.

In some embodiments, low-latency consumers may not want to or be able to consume a low-latency stream (408 a) directly. For example, the stream might contain personally-identifiable fields that need to be restricted to specific consumers or the final consumer may need additional processing of events for their use. As another example, the consumer may be consuming from many sources and is unable to handle different event schemas of their various inputs. In these scenarios, the system (400) provides derived low-latency streams, or “filters”, that have all of the events (or at least all of the desired events) as the second queue (408 b) stream. Each filter can be associated with a quality of service (QoS) level. In the illustrated embodiment, three QoS levels are provided: “at least once”, “at most once”, and “at least once with tag.”

A filter having an at least once QoS outputs every event but potentially includes duplicates. In the event of a system (400) failure, the at least once filter resends previously-sent events. A filter having an at most once QoS does not include duplicates but potentially drops data. The at most once filter does not reprocess the same event batch more than once.

Finally, a filter having an at least once with tag QoS generates batch dataset wherein each event in the batch includes tags allowing downstream consumer systems to detect duplicates. In one embodiment, this filter includes a stream topic, partition, and a “cursor,” that can be used to detect duplicates. In some embodiments, Kafka offsets and CMS Message Ids could provide such cursors. The consumer system is then responsible for keeping track of the last cursor it processed, and discard any subsequent batch with a cursor less than or equal the new batch. This requires a 1-to-1 correspondence between batches in the pipeline and derived streams.

Each of the above filters may be implemented via a separate stream processor (e.g., stream topology). In these embodiments, the filters utilize an output of the system (400) (e.g., queues 408 a, 408 b) as an input source (e.g., spout) and output the filtered feed.

For the at least one filter, the filter will always back up in the event of a failure and resend any events that cannot be confirmed as being successfully delivered. This filter uses the initial spout (404) and streaming queue (408 b) as inputs (e.g., filter spouts). In this embodiment, the consumer is configured to not report its current read offset. When sending data, the filter spout includes the current events cursor in a message identifier. The receiver (e.g., sink) would then acknowledge the received message only after successfully delivering the filtered output to the derived stream. In some embodiments, the receiver could also use the existing spooler logic to fail a tuple if it can't deliver it, and then continue to fail subsequent tuples until it receives a restarting indication from the spout. Upon receipt of an acknowledgement, the filter spout would commit that cursor back to the system (400). On receipt of a fail of a sent event, the filter spout would back up the received offset to a cursor at or before the last acknowledged event and restart sending.

For the at most once filter, the filter spout enables automatically committing offsets in a stream queue. By turning on auto-commitment, the filter spout only transmits a given event once and does not re-transmit events causing duplication.

For the at least once with tag filter, the at least one filter mechanism can be used. However, in this filter, tags will be added prior to transmission to the consumer. These tags include the cursor, as described above, but also a topic and partition if they aren't implied by the derived stream's partition.

In some embodiments, an exactly once filter may be implemented based on the at least once with tag filter. In this embodiment, a receipt acknowledgement message can be saved as reliably as the system (400) can support. Additionally, the filter, on receipt of the acknowledgement, could update some persistent record of the delivered cursor. However, persisting this data may be computationally expensive and require significant storage. In an alternative embodiment, given the at least once with tag filter, the filter, on a start-up or after a failure, can access the output stream and read back a plurality of last-sent messages in the queue. The filter could then determine the tag of the last message written, then discard any replayed events from the spout until it was caught up, thus ensuring exactly once delivery.

Within the core business logic of the stream processor (304) various fields may be added to the output schema versus the emitted schema. As used herein, output schema refers to the schema used by files generated by the pipeline. An output schema includes defaults allowing schema migration. An emitted schema refers to the schema used by event emitters when publishing to a data highway. The emitted schema may contain required fields without defaults.

In existing pipelines, when the event emitter updates the schema of their data, changes to the stream processor topology must be made to account for the changed schema. This is because of the way a topology in existing pipelines is defined: the inputs and outputs need to be laid out in advance.

In some embodiments of the illustrated pipeline (400), the stream processor (304) may only require a handful of common fields from the input events to perform business logic and computations (e.g., joins, deduplication, etc.). The following embodiments provide a novel optimization that only extracts the needed fields from events in the input stream and serializes the entire event. This serialized event is then included as a hidden field and passed-through the stream processor (304) along with the required fields. After the processing is performed on the required fields, the stored serialized event is de-serialized, and its schema and fields are updated with the new modifications performed in the topology. This optimization results in speedup when few fields are used, and additionally allows for automatic schema migration when the emitted schema changes, with no need to update business logic within the stream processor.

In addition to the foregoing, the disclosed embodiments avoid processing an entire event that is encoded in slower serialized formats such as Avro. This speed up is due to avoiding the need to deserialize events in each processing stage of a stream processor (304). Further, whenever changes are made to the emitted schema, code changes to the stream processor (304) are not required in order to understand the new schema since only the common, required fields are used.

FIG. 5 is a flow diagram illustrating a method for processing events in a streaming pipeline to support automatic schema upgrades according to some embodiments of the disclosure.

In step 502, the method (500) extracts needed fields from events in an input stream of events. In some embodiments, a stream processor (304) may only require a limited number of fields to perform processing. For example, the stream processor (304) may need an event identifier, a join key, or other similar fields for processing. The specific fields are not limiting. The event, however, will include many other fields that may not be needed for processing by the stream processor (304) but are nonetheless interesting to the consumers. Thus, in step 502, the method (500) first identifies these fields and extracts them from the event. In one embodiment, step 502 may be performed by a processing stage of the stream processor (304). In one embodiment, this processing stage comprises the first stage of the stream processor (304) and is referred to as the “projector” or “projector stage.” The projector performs steps 502, 504, and 506, and passes the event generated in step 506 to the next stages of the stream processor.

In step 504, the method (500) serializes the entire event, including the needed fields. In the illustrated embodiment, the method (500) serializes the entire event, including every received field. The specific serialization algorithm is not limited. In some embodiments, the serialization converts the event into a compacted form for data transmission and thus reduces network bandwidth.

In step 506, the method (500) includes the serialized event in a hidden field of a compacted event and also inserts the needed fields into the same compacted event. As used herein, a “compacted event” is used to distinguish between events processed by the stream processor (304) (“compacted”) after the projector stage and the events original received by the projector stage. In general, the same format may be used for both events. However, as will be discussed, the compacted event generally includes fewer total fields than the original event received in step 502.

As one example, the method (500) initializes an empty compacted event and populates the needed fields and their values into the compacted event. The method (500) then creates a hidden field (e.g., “_original”) as the final field. The specific format or mechanism for creating the hidden field may vary depending on the underlying event format (e.g., Avro, ORC, etc.). In general, the use of a hidden field guarantees that the field will not be processed by any downstream processing stage. The method (500) then sets the value of this hidden field to be the serialized event.

In some embodiments, the method (500) further includes the identity of the emitted schema as a non-serialized field in the compacted event. This schema value may then be used to output the event according to the output schema as described herein.

In step 508, the method (500) performs stream processing on the compacted event via the needed fields. In the illustrated embodiment, the processing may comprise any processing described previously. However, in the illustrated embodiment, the processing is only performed using the needed fields. During processing, the stream processor will add additional fields/values as the event is processed: computed values, dimensions looked up from fact tables, traffic protection results, etc. These fields and values are added to the compacted event as described previously. As a result, at the end of step 508, the method (500) generates a compacted event potentially including one or more additional fields or changed values.

In step 510, the method (500) deserializes the hidden field. In the illustrated embodiment, step 510 is executed after stream processing. Thus, all the needed fields (which are deserialized) have been processed as needed and potentially new fields have been added. In step 510, the method (500) deserializes the hidden field to obtain the original event. In some embodiments, the method (500) maintains the original event in memory as the original event and the compacted event may include duplicate fields since some fields were changed during processing. For example, the original event may include a price in dollars, this field (“price”) may be selected as a needed field and processed to convert the currency to Euro. Thus, after deserializing in step 510, the method (500) will include the processed field (in Euro) and the original field (in dollars).

In step 512, the method (500) updates the fields of the event based on an output schema. In the illustrated embodiment, from the final event delivered from the stream processor, the method (500) determines an output event schema based on the input schema (which is included in the compacted event). The output schema generally includes all fields from the input schema and, in some embodiments, includes a location to save all of the values generated within the stream processor. The method (500) then creates an output event using the output schema from the original serialized event plus any values added within the stream processor. Continuing with the previous example, the output schema may state that the processed price (in Euro) should overwrite the original price (in dollars). Alternatively, the output schema may state that the processed price should be added as a new field (“currency_converted_price”). Details of steps 510 and 512 are provided in more detail in FIG. 6A and that disclosure is incorporated herein.

In addition to supporting schema migration, the method (500) is much more efficient than processing raw events. However, as will be discussed, modifications may be needed to support explosion operations (described previously). Specifically, since the original serialized event is passed through, the system should ensure that only the appropriate exploded event goes to the streaming queues (408 a, 408 b). FIGS. 6B and 6C provide alternative techniques for making this guarantee.

FIG. 6A is a flow diagram illustrating a method for reserializing events in a streaming pipeline to support automatic schema upgrades according to some embodiments of the disclosure.

In the illustrated method (600 c), a decoder and encoder pair is selected for any output schema identified for a given emitted schema. This decoder-encoder pair is then used to generate the resulting output event.

In step 602 a, the method (600 a) determines an output schema based on an emitted schema. In one embodiment, the emitted schema is extracted from an event output by the stream processing stages. As described above, in some embodiments, the event is annotated with a field that includes an identifier of the emitted schema associated with the original event. This value is extracted from the event and used to identify the corresponding output table. In some embodiments, the method (600 a) maintains a mapping of input schemas to output schemas. For example, this mapping may be stored in a distributed key-value store (e.g., Apache® HBase) or similar data store. In most embodiments, the output schema is a version of the emitted schema with a location for any additional values generated by the stream processor.

In step 604 a, the method (600 a) determines if an encoder exists for the identified output schema. If not, the method (600 a) generates the encoder in step 606 a and selects the encoder in step 608 a. If the method (600 a) determines that an encoder has already been generated for a given output schema, the method (600 a) proceeds to select the previously-generated encoder in step 608 a.

The generated and selected encoder for a given output schema handles serializing the event output by the stream processor once the values to go into the event have been determined during processing. In one embodiment, an encoder corresponds to one Avro Record schema. In this embodiment, the encoder allocates slots in object array fields in the record and builds a list of encoder objects to serialize the object values in the proper form. For example, an integer encoder pulls an integer value from the object array and serializes it to the output event, handling nullable fields and default values as appropriate. For simple scalar values, a similar copying and null-check occurs. For arrays of data, the object array includes a list of values, and the serializer object creates an array element (e.g., in the preceding example, an Avro Array), serializes the values from the array. In some embodiments, there may also be a serializer that understands serialization of maps from a map object stored in the object array to a map in the output schema.

In the illustrated embodiment, embedded records, whether singleton, array, or map values, are handled by embedded encoder objects. In that case, the parent encoder's object array entry contains an object array for the embedded encoder. Alternatively, the parent encoder's object array entry may contain a list of object arrays for a list of records, or the map values are object arrays for a map of records. In one embodiment, the parent encoder invokes the embedded encoder to encode the embedded record.

In step 610 a, the method (600 a) determines if a decoder exists for the identified output schema. If not, the method (600 a) generates the decoder in step 612 a and selects the decoder in step 614 a. If the method (600 a) determines that a decoder has already been generated for a given output schema, the method (600 a) proceeds to select the previously-generated decoder.

In one embodiment, the decoder identifies the correspondence between fields in the emitted schema and fields in the output schema. The decoder then builds a list of decoders that deserialize a value from the record output by the stream processor and stores the result in the encoder's object array. As with the encoder, the decoder may include decoders that understand complex values, including arrays, maps. In some embodiments, the decoder includes embedded decoders to handle embedded records on input.

In step 616 a, the method (600 a) invokes the decoder on the event output by the stream processing. In one embodiment, the decoder steps through each field of the event and deserializes the original event fields into the encoders object array. In the illustrated embodiment, the decoder does not deserialize the fields generated by the stream processor as these fields may already be deserialized.

In step 618 a, the method (600 a) inserts any additional needed fields generated during stream processing. In the illustrated embodiment, the method (600 a) determines if any additional needed fields are included in the output event.

In step 620 a, the method (600 a) encodes the event using the encoder. In step 620 a, the encoder walks through its list of field encoders, calling each to encode its value. In one embodiment, each encoder serializes its value as appropriate, including complex objects.

In the foregoing method (600 a), the resulting output event comprises a serialized event according to a defined output schema. While the foregoing methods (500, 600 a) operate on single events, additional processing may be implemented to support explosion operations.

For an event that triggers an explosion operation, there's an underlying assumption that the emitted event includes an array of records, and each result from the explosion should be identical to the input event, but populated with only one of the records from the original array. However, at the conclusion of the decoder phase (step 616 a), the appropriate element in the encoder's object array has a list of object arrays, one for each embedded record. Let's assume we want to create an output even with just one of those records. Thus, the overall goal to support an explosion operation would be to replace that list of arrays to a list with just one array. The resulting encoder run would generate an output with just one record. FIGS. 6B and 6C describe two alternative techniques for achieving this goal.

FIG. 6B is a flow diagram illustrating a method for processing explosion operations in a streaming pipeline to support automatic schema upgrades according to some embodiments of the disclosure.

In step 602 b, the method (600 b) receives a combined event. In one embodiment, a combined event comprises an event that itself includes an array of additional events. As one example, a combined event may comprise a set of fields describing an advertising creative with an array of objects that describe particular instances in which that creative was displayed. Since the ad creative data is constant, it is included once while the varying data is included in the array.

In step 604 b, the method (600 b) explodes the event. In one embodiment, the explosion can simply comprise extracting each record in the array of events. However, in some embodiments, the method uses a set of shared event properties (e.g., the ad creative properties) and generates exploded events that include these shared events and fields from each of the objects in the array of events.

In step 606 b, the method (600 b) adds an index to each exploded event and serializes the combined event. This serialized event is then written to a hidden field in the exploded event. In the illustrated embodiment, the index refers to the position of the exploded event in the array of additional events. In some embodiments, the method (600 b) additionally includes the length of the array to enable paging. Thus, after step 606 b, a set of n events for a given combined event are generated. Each of the n events includes an index (i of n) and a hidden copy of the serialized combined event.

In step 608 b, the method (600 b) processes the exploded events in a stream processor. In one embodiment, step 608 b includes the steps described in FIG. 5 , which are not described herein. Specifically, step 608 b may include steps 502 through 508 of the method (500). In brief, the method (600 b) may be executed as the first stage in the stream processor, and may be transparent to other steps described in FIG. 5 .

In step 610 b, the method (600 b) extracts the corresponding serialized exploded event from the serialized combined event. As described above, after processing, the method (600 c) receives the processed exploded event. Since the original combined event was stored in a hidden field, the method (600 b) detects this hidden field and deserialized the original, combined event. This deserialized event includes all details of each exploded event, including the received exploded event. The method (600 b) utilizes the index to locate the original copy of the pre-exploded event (in the array of events) and uses this event as the corresponding serialized exploded event. In this manner, the method (600 b) can “reconstruct” the original exploded event after the event was processed in the stream processor.

In step 612 b, the method (600 b) discards the other events in the array that do not correspond to the processed, exploded event. These discarded events comprise exploded events other than the processed events. At the end of step 612 b, the method (600 b) obtains the original exploded event prior to stream processing as well as a processed version of the same event.

In step 614 b, the method (600 b) reserializes the event. In one embodiment, this reserialization is performed in the manner described in step 512 and FIG. 6A. Since the event appears to the decoder-encoder as a standard event as described above, it can be reserialized by the same process as previously described.

FIG. 6C is a flow diagram illustrating an alternative method for processing explosion operations in a streaming pipeline to support automatic schema upgrades according to some embodiments of the disclosure.

In step 602 c, the method (600 c) receives a combined event. In one embodiment, a combined event comprises an event that itself includes an array of additional events. As one example, a combined event may comprise a set of fields describing an advertising creative with an array of objects that describe particular instances in which that creative was displayed. Since the ad creative data is constant, it is included once while the varying data is included in the array.

In step 604 c, the method (600 c) decodes the combined event. In this step, the method (600 c) uses the decoder described in steps 610 a-614 a of FIG. 6A. The method (600 c) then encodes each individual event (606 c) using the encoder described in steps 604 a-608 a of FIG. 6A. After step 606 c, the event comprises a decoded (deserialized) array of serialized events that correspond to the exploded events described in FIG. 6B. Importantly, each serialized event is independent and does not rely on the shared fields for processing. Thus, the serialized exploded events include significant duplication of shared fields. As such, the method (600 c) explodes the event up front.

In step 606 c, the method (600 c) indexes each of the serialized events similar to that described in step 606 b.

In step 608 c, the method (600 c) transmits each serialized event to the stream processor. Since each event was exploded “up front,” the method (600 c) can execute the method (500) without change as part of step 608 c.

The first method (600 b) explodes events during reserialization that is, after processing. The second method (600 c) performs explosion “up front,” prior to stream processing. Explosion up front would have least impact on the rest of the stream processor. Existing components would work as is, and the serialized event byte arrays going through the stream processor would be smaller. It does, however, mean that projectors would have to deserialize the common fields separately for each exploded event. It also requires adding an additional processing stage up front. In contrast, selecting the appropriate record at the end would also have relatively little impact on the stream processor, and would avoid additional processing stages at the start of stream processing. However, when performing explosion at the end of processing the serialized event passed through the stream processor would be larger, since exploded event would carry all of the serialized input events. This would be a particular concern if the explosion rate is high. Additionally, end-processing may complicate join operations, where a secondary event joins with a particular instance of an exploded primary. Thus, the selection between the methods (600 b, 600 c) may be made based on the needs of the pipeline.

In some embodiments, the implementation of automatic schema upgrades described above may place additional requirements on event emitters, some of which are summarized below.

First, any release of an emitted schema must have a corresponding output schema. The output schema would include anything the downstream consumer wants passed through, plus any fields that will be added by the stream processor. Second, how and where those fields are placed in the output may vary, but the fields shouldn't be moved around in the output schema without coordinating the system operator. Third, an event emitter shouldn't emit using the new schema until both schemas are available in a system schema registry. Fourth, if the reader schema isn't available, the pipeline may not be able to process the event at all. If a writer schema can't be found, the pipeline may process the event, but may not generate an output. In some embodiments, a compiled-in default output schema may be used instead. Further, in some embodiments, the auditor, when generating the final output for a batch, may identify the output schema name. In this embodiment, a data highway application programming interface (API) may return all of the versions of a schema name. Using this API, the auditor may find the latest version of the output schema and use that for all events in a given batch. Sixth, in some embodiments, there is a deterministic way to derive the output schema from the emitted schema, such as an annotation in the emitted schema or a naming convention. Seventh, the output schema must (at least should) be reader/writer schema compatible with all writer schemas. In other words, the system may use the output schema as reader schema when deserializing any serialized event. Eighth, if the foregoing isn't possible, the system may implement stream processor-specific logic to transform the input event into an output event. Ninth, the reader/writer schema requirement may require putting a joined primary in a sub-record of the secondary. Tenth, deserialization with the current output schema should work with anything serialized with a current or previous emitted schema. Eleventh, an event emitter should not change a field's type. Twelfth, an event emitter should not move a field around from one sub-record to another. Thirteenth, while the emitting schema may have non-nullable fields, the output schema must have all nullable fields.

In some embodiments, before the methods write to the streaming queues (408 a, 408 b), the stream processor may merge of the input event(s) and generated fields and produce an output serialized with the appropriate output schema. The serialized output event (and schema name/version) will be part of the event written to the streaming queues (408 a, 408 b). The events ultimately written to the file system may be in the same format. The batches written to the streaming queues (408 a, 408 b) or read from the spooler (308) may include information useful to the auditor (310) and the schema name/version/blob of the final event.

In contrast to declaring the complete set of fields in the stream processor, event in the stream processor may only include the complete serialized original event with its schema name and version. In some embodiments, the serialized event may comprise a byte blob passed along to the output and not processed again within the stream processor. In one embodiment, the stream processor may compress the blob if it's large, or based on event type. If so, the event may include a field indicating whether the blob is compressed or not. In some embodiments, if the event this is a secondary that will join to a primary, the primary is included similarly to the above: schema name/version and serialized bytes. In some embodiments, a set of fields may be defined that are actually used in the stream processor. For example, an enumeration for each set of needed fields may be included. This field would include any fields needed in the stream processor, for example for lookups or traffic protection, plus any values generated within the stream processor. In some embodiments, on receipt of the event, any fields needed in the stream processor will be pulled from the event. In some embodiments, the still-serialized original byte blob may be passed through intact.

FIG. 7 is a schematic diagram illustrating a computing device showing an example embodiment of a client or server device used in the various embodiments of the disclosure.

The computing device (700) may include more or fewer components than those shown in FIG. 7 . For example, a server computing device may not include audio interfaces, displays, keypads, illuminators, haptic interfaces, GPS receivers, cameras, or sensors.

As shown in the figure, the device (700) includes a processing unit (CPU) (722) in communication with a mass memory (730) via a bus (724). The computing device (700) also includes one or more network interfaces (750), an audio interface (752), a display (754), a keypad (756), an illuminator (758), an input/output interface (760), a haptic interface (762), an optional global positioning systems (GPS) receiver (764) and a camera(s) or other optical, thermal, or electromagnetic sensors (766). Device (700) can include one camera/sensor (766), or a plurality of cameras/sensors (766), as understood by those of skill in the art. The positioning of the camera(s)/sensor(s) (766) on the device (700) can change per device (700) model, per device (700) capabilities, and the like, or some combination thereof.

The computing device (700) may optionally communicate with a base station (not shown), or directly with another computing device. Network interface (750) is sometimes known as a transceiver, transceiving device, or network interface card (NIC).

The audio interface (752) produces and receives audio signals such as the sound of a human voice. For example, the audio interface (752) may be coupled to a speaker and microphone (not shown) to enable telecommunication with others or generate an audio acknowledgment for some action. Display (754) may be a liquid crystal display (LCD), gas plasma, light-emitting diode (LED), or any other type of display used with a computing device. Display (754) may also include a touch-sensitive screen arranged to receive input from an object such as a stylus or a digit from a human hand.

Keypad (756) may comprise any input device arranged to receive input from a user. Illuminator (758) may provide a status indication or provide light.

The computing device (700) also comprises input/output interface (760) for communicating with external devices, using communication technologies, such as USB, infrared, Bluetooth™, or the like. The haptic interface (762) provides tactile feedback to a user of the client device.

Optional GPS transceiver (764) can determine the physical coordinates of the computing device (700) on the surface of the Earth, which typically outputs a location as latitude and longitude values. GPS transceiver (764) can also employ other geo-positioning mechanisms, including, but not limited to, triangulation, assisted GPS (AGPS), E-OTD, CI, SAI, ETA, BSS, or the like, to further determine the physical location of the computing device (700) on the surface of the Earth. In one embodiment, however, the computing device (700) may through other components, provide other information that may be employed to determine a physical location of the device, including, for example, a MAC address, Internet Protocol (IP) address, or the like.

Mass memory (730) includes a RAM (732), a ROM (734), and other storage means. Mass memory (730) illustrates another example of computer storage media for storage of information such as computer-readable instructions, data structures, program modules, or other data. Mass memory (730) stores a basic input/output system (“BIOS”) (740) for controlling the low-level operation of the computing device (700). The mass memory also stores an operating system (741) for controlling the operation of the computing device (700)

Applications (742) may include computer-executable instructions which, when executed by the computing device (700), perform any of the methods (or portions of the methods) described previously in the description of the preceding Figures. In some embodiments, the software or programs implementing the method embodiments can be read from hard disk drive (not illustrated) and temporarily stored in RAM (732) by CPU (722). CPU (722) may then read the software or data from RAM (732), process them, and store them to RAM (732) again.

For this disclosure, a module is a software, hardware, or firmware (or combination thereof) system, process or functionality, or component thereof. A module performs or facilitates the processes, features, or functions described herein (with or without human interaction or augmentation). A module can include sub-modules. Software components of a module may be stored on a computer-readable medium for execution by a processor. Modules may be integral to one or more servers or be loaded and executed by one or more servers.

The terms “user,” “subscriber,” “consumer” or “customer” refer to a user of an application or applications as described herein or a consumer of data supplied by a data provider. By way of example, and not limitation, the term “user” or “subscriber” can refer to a person who receives data provided by the data or service provider over the Internet in a browser session, or can refer to an automated software application which receives the data and stores or processes the data.

One of skill in the art may implement the methods and systems of the present disclosure in many manners. As such, the disclosed embodiments are not to be limited by the preceding exemplary embodiments and examples. In other words, functional elements being performed by single or multiple components, in various combinations of hardware and software or firmware, and individual functions, may be distributed among software applications at either the client level or server level or both. In this regard, one may combine any number of the features of the different embodiments described herein into single or multiple embodiments, and alternate embodiments having fewer than or more than, all the features described herein are possible.

Functionality may also be, in whole or in part, distributed among multiple components, in manners now known or to become known. Thus, myriad software/hardware/firmware combinations are possible in achieving the functions, features, interfaces, and preferences described herein. Moreover, the scope of the present disclosure covers conventionally known manners for carrying out the described features and functions and interfaces. The scope of the present disclosure may also cover variations and modifications made to the hardware or software or firmware components described herein as would be understood by those skilled in the art.

Furthermore, the embodiments of methods presented and described as flowcharts in this disclosure are provided by way of example to provide a complete understanding of the technology. The disclosed methods are not limited to the operations and logical flow presented herein. Alternative embodiments exist that alter the order of the various operations or include independent sub-operations that are part of a more extensive operation.

While the disclosure describes various embodiments, such embodiments should not limit the teaching of this disclosure to those embodiments. Various changes and modifications may be made to the elements and operations described above to obtain a result that remains within the scope of the systems and processes described in this disclosure. 

What is claimed is:
 1. A method comprising: receiving an event, the event including a plurality of fields; determining a set of needed fields used by a downstream processing stage of a streaming processor from the plurality of fields based on an upgrade schema migration modification; extracting the set of needed fields from the plurality of fields; generating a plurality of serialized fields by serializing the plurality of fields; generating a new event, the new event including the set of needed fields and a hidden field, the value of the hidden field comprising the serialized fields; transmitting the new event to at least one processing stage of a stream processor; generating a reserialized event by reserializing a processed event generated by the stream processor, the processed event generated by the stream processor based on the new event; and outputting the reserialized event to a downstream consumer.
 2. The method of claim 1, the reserializing the processed event comprising: deserializing the hidden field to generate a deserialized event; performing an update operation selected from the group consisting of: updating one or more fields of the deserialized event based on the needed fields, and adding one or more fields to the deserialized event based on the needed fields.
 3. The method of claim 1, the performing an update operation comprising selecting the update operation based on an output schema.
 4. The method of claim 1, the generating the new event further comprising inserting a value representing an emitted schema into the new event, the emitted schema comprising a schema of the received event.
 5. The method of claim 4, the reserializing the processed event comprising generating a decoder-encoder pair based on the emitted schema and an output schema associated with the emitted schema.
 6. The method of claim 1, the event comprising an exploded event, the event including a serialized copy of a combined event including the exploded event, the generating the reserialized event further comprising deleting at least one other exploded event in the combined event during the reserializing.
 7. The method of claim 1, the event comprising an exploded event, the exploded event generated by: detecting that a combined event requires explosion; deserializing the combined event; and generating a set of exploded events including the event, each exploded event being serialized and indexed based on the combined event.
 8. A non-transitory computer-readable storage medium for tangibly storing computer program instructions capable of being executed by a computer processor, the computer program instructions defining the steps of: receiving an event, the event including a plurality of fields; determining a set of needed fields used by a downstream processing stage of a streaming processor from the plurality of fields based on an upgrade schema migration modification; extracting the set of needed fields from the plurality of fields; generating a plurality of serialized fields by serializing the plurality of fields; generating a new event, the new event including the set of needed fields and a hidden field, the value of the hidden field comprising the serialized fields; transmitting the new event to at least one processing stage of a stream processor; generating a reserialized event by reserializing a processed event generated by the stream processor, the processed event generated by the stream processor based on the new event; and outputting the reserialized event to a downstream consumer.
 9. The computer-readable storage medium of claim 8, the reserializing the processed event comprising: deserializing the hidden field to generate a deserialized event; performing an update operation selected from the group consisting of: updating one or more fields of the deserialized event based on the needed fields, and adding one or more fields to the deserialized event based on the needed fields.
 10. The computer-readable storage medium of claim 8, the performing an update operation comprising selecting the update operation based on an output schema.
 11. The computer-readable storage medium of claim 8, the generating the new event further comprising inserting a value representing an emitted schema into the new event, the emitted schema comprising a schema of the received event.
 12. The computer-readable storage medium of claim 11, the reserializing the processed event comprising generating a decoder-encoder pair based on the emitted schema and an output schema associated with the emitted schema.
 13. The computer-readable storage medium of claim 8, the event comprising an exploded event, the event including a serialized copy of a combined event including the exploded event, the generating the reserialized event further comprising deleting at least one other exploded event in the combined event during the reserializing.
 14. The computer-readable storage medium of claim 8, the event comprising an exploded event, the exploded event generated by: detecting that a combined event requires explosion; deserializing the combined event; and generating a set of exploded events including the event, each exploded event being serialized and indexed based on the combined event.
 15. An apparatus comprising: a processor; and a storage medium for tangibly storing thereon program logic for execution by the processor, the stored program logic causing the processor to perform the operations of: receiving an event, the event including a plurality of fields; determining a set of needed fields used by a downstream processing stage of a streaming processor from the plurality of fields based on an upgrade schema migration modification; extracting the set of needed fields from the plurality of fields; generating a plurality of serialized fields by serializing the plurality of fields; generating a new event, the new event including the set of needed fields and a hidden field, the value of the hidden field comprising the serialized fields; transmitting the new event to at least one processing stage of a stream processor; generating a reserialized event by reserializing a processed event generated by the stream processor, the processed event generated by the stream processor based on the new event; and outputting the reserialized event to a downstream consumer.
 16. The apparatus of claim 15, the reserializing the processed event comprising: deserializing the hidden field to generate a deserialized event; performing an update operation selected from the group consisting of: updating one or more fields of the deserialized event based on the needed fields, and adding one or more fields to the deserialized event based on the needed fields.
 17. The apparatus of claim 16, the generating the new event further comprising inserting a value representing an emitted schema into the new event, the emitted schema comprising a schema of the received event.
 18. The apparatus of claim 17, the reserializing the processed event comprising generating a decoder-encoder pair based on the emitted schema and an output schema associated with the emitted schema.
 19. The apparatus of claim 16, the event comprising an exploded event, the event including a serialized copy of a combined event including the exploded event, the generating the reserialized event further comprising deleting at least one other exploded event in the combined event during the reserializing.
 20. The apparatus of claim 16, the event comprising an exploded event, the exploded event generated by: detecting that a combined event requires explosion; deserializing the combined event; and generating a set of exploded events including the event, each exploded event being serialized and indexed based on the combined event. 